Massachusetts Congressman Ed Markey can't seem to tell when he's winning. Markey, one of the House's leading global warming warriors, brutalized the domestic automobile industry last fall for not doing enough to curb America's consumption of gasoline.

His efforts helped lead to tough new fuel economy standards.

But now Markey, a Democrat, is going after another industry that has done more than any other in the last few months to reduce the demand for oil, if inadvertently.

Markey hauled oil company executives before his committee this week to demand an accounting for their record profits, due largely to the soaring price of oil. He threatened the companies with tax penalties unless they roll back the profits, which also would have the effect of lowering gasoline prices.

Markey is working against himself.

In the six weeks ending March 1, gasoline consumption in the United States fell 1.1 percent as prices moved well above $3 a gallon. That's the longest stretch of reduced gasoline demand in 16 years.

At the same time, March saw consumers choosing more fuel efficient cars over light trucks and sport utility vehicles for the first time since 2002, according to Autodata.

That should tell Markey that price is the most efficient regulator of fuel economy.

Rather than beat up on automotive and oil industry executives, Markey ought to initiate a serious discussion in Congress about whether higher gasoline prices are in the national interest.

The trends of the last several weeks seem to indicate that higher prices diminish demand. If burning less oil is the goal, Markey and his colleagues should seriously consider a floating tax that would keep gasoline prices at the level determined to be the most effective in reducing fuel use.

There would be a political price, of course. But it's no greater than the one Congress is asking industry to pay. It would also help create a market for the small vehicles Congress wants Detroit to build.

Congress is asking industry to do some hard things to meet the nation's energy goals. It should be willing to do the same.